Call the endpoint to issue a new token with an authorization code

Oct 13, 2025 by talynt.org 56 views

Error when creating refresh token: value too long for type character varying(255)

Introduction

When working with OAuth2 in Django, creating a new refresh token using a custom token generator can sometimes result in a django.db.utils.DataError: value too long for type character varying(255) error. This issue arises when attempting to insert a value that exceeds the column size in the database. In this article, we will delve into the causes of this error and explore possible solutions to resolve it.

Describe the Bug

When trying to create a new refresh token using OAuth2 in Django with a custom token generator, the application throws a django.db.utils.DataError: value too long for type character varying(255) error. This error seems to be caused by attempting to insert a value that exceeds the column size in the database.

To Reproduce

To reproduce this behavior, follow these steps:

Call the endpoint to issue a new token with an authorization code: This will trigger the creation of a refresh token.
The error value too long for type character varying(255) is thrown: This error occurs specifically during the creation of a refresh token in the oauth2_provider/oauth2_validators.py file.

Expected Behavior

The expected behavior is that the refresh token should be created successfully without the database column size being a problem.

Version

We have tested this issue with the latest published release of django-oauth-toolkit and it's still a problem.

Additional Context

The error occurs specifically during the creation of a refresh token in the oauth2_provider/oauth2_validators.py file. It seems that the RefreshToken model might need its column size increased or additional validation added to ensure the token length fits the database constraints.

Possible Solutions

To resolve this issue, we can try the following solutions:

1. Increase the column size of the RefreshToken model

We can increase the column size of the RefreshToken model to accommodate longer token lengths. This can be done by modifying the RefreshToken model in the oauth2_provider/models.py file.

class RefreshToken(models.Model):
    # ...
    token = models.CharField(max_length=512)  # Increase the max_length from 255 to 512
    # ...

2. Add additional validation to the RefreshToken model

We can add additional validation to the RefreshToken model to ensure that the token length fits the database constraints. This can be done by creating a custom validation function in the oauth2_provider/validators.py file.

from django.core.exceptions import ValidationError

def validate_refresh_token(token):
    if len(token) > 255:
        raise ValidationError("Token length exceeds the maximum allowed length")

3. Use a custom token generator

We can use a custom token generator that generates tokens of a fixed length, ensuring that they fit within the database constraints. This can be done by creating a custom token generator in the oauth2_provider/token_generators.py file.

import secrets

def custom_token_generator():
    return secrets.token_urlsafe(32)  # Generate a token of fixed length 32

Conclusion

In conclusion, the django.db.utils.DataError: value too long for type character varying(255) error when creating a refresh token using OAuth2 in Django with a custom token generator can be resolved by increasing the column size of the RefreshToken model, adding additional validation to the RefreshToken model, or using a custom token generator that generates tokens of a fixed length. By implementing one of these solutions, we can ensure that the refresh token is created successfully without the database column size being a problem.

Related Issues

References

Django OAuth Toolkit documentation
Django database constraints documentation
Error when creating refresh token: value too long for type character varying(255) - Q&A

Introduction

In our previous article, we discussed the issue of creating a refresh token using OAuth2 in Django with a custom token generator resulting in a django.db.utils.DataError: value too long for type character varying(255) error. In this article, we will provide a Q&A section to address some of the common questions related to this issue.

Q&A

Q: What is the cause of the `django.db.utils.DataError: value too long for type character varying(255)` error?

A: The error occurs when attempting to insert a value that exceeds the column size in the database. In this case, the column size is set to character varying(255) which means it can only accommodate values up to 255 characters.

Q: How can I increase the column size of the RefreshToken model?

A: You can increase the column size of the RefreshToken model by modifying the RefreshToken model in the oauth2_provider/models.py file. For example, you can change the max_length from 255 to 512.

class RefreshToken(models.Model):
    # ...
    token = models.CharField(max_length=512)  # Increase the max_length from 255 to 512
    # ...

Q: What is the difference between `character varying(255)` and `varchar(255)`?

A: character varying(255) and varchar(255) are both used to define a character field in a database, but they have slightly different meanings. character varying(255) is a PostgreSQL-specific syntax, while varchar(255) is a more general syntax that can be used in multiple databases. In Django, you can use either syntax, but character varying(255) is the default.

Q: Can I use a custom token generator to generate tokens of a fixed length?

A: Yes, you can use a custom token generator to generate tokens of a fixed length. For example, you can use the secrets module in Python to generate a token of a fixed length.

import secrets

def custom_token_generator():
    return secrets.token_urlsafe(32)  # Generate a token of fixed length 32

Q: How can I add additional validation to the RefreshToken model?

A: You can add additional validation to the RefreshToken model by creating a custom validation function in the oauth2_provider/validators.py file. For example, you can create a function that checks if the token length exceeds the maximum allowed length.

from django.core.exceptions import ValidationError

def validate_refresh_token(token):
    if len(token) > 255:
        raise ValidationError("Token length exceeds the maximum allowed length")

Q: What are some best practices for handling token lengths in OAuth2?

A: Some best practices for handling token lengths in OAuth2 include:

Using a fixed length for tokens to ensure consistency and avoid issues with database constraints.
Implementing additional validation to check if the token length exceeds the maximum allowed length.
Using a custom token generator to generate tokens of a fixed length.
Regularly reviewing and updating token lengths to ensure they remain secure and compliant with industry standards.